The present invention relates to a DC type gas-discharge display panel and a gas-discharge display apparatus with employment of the DC type gas-discharge display panel.
First of all, the publications related to the present invention are listed as follows:
(1). "A 17-in High Resolution DC Plasma Display" by Niwa et al., The Journal of the Institute of Television Engineers of Japan, Vol. 44, No. 5 (1990) pp. 571-577.
(2). "A 20-in Color DC Gas-Discharge Panel for TV Display" by Murakami et al., IEEE Transactions on Electron Devices, Vol. 36, No. 6, June 1989, pp. 1063-1072.
(3). "Ultra-Low Reflectivity Color Display Gas-Discharge Panel" by Sakai et al., The Journal of the Institute of Television Engineers of Japan Vol. 42, No. 10 (1988) pp. 1084-1090.
(4). U.S. Pat. No. 4,780,644, "Gas-Discharge Display Panel".
(5). "Plasma Display Panel with a Resistor in each Cell" by Takano et al., Annual Convention of Institute of Television Engineers of Japan, 1990, Provisional Report 4-3, pp. 77-78.
As a first conventional DC type gas-discharge panel, it has been utilized such a structure thereof as shown in FIGS. 1A and 1B. FIG. 1A is a sectional view of this first conventional gas-discharge panel, and FIG. 1B is a plan view thereof, as viewed from a display side. In FIGS. 1A and 1B, symbol "FP" indicates a front plate (glass); symbol "BM" shows a black grid (black matrix); symbol "BA" is a partition; symbol "A" shows an anode (indium tin oxide); symbol "Ph" denotes phosphor; symbol "C" shows a cathode (Ni); symbol "D" indicates a dielectric material; symbol "TH" denotes a third electrode; and symbol "RP" shows a rear plate (glass). A detailed explanation of this gas-display panel is described in the above-described publication (1). In this panel, the display panel of the X-Y matrix is driven by the 1-line at-a-time drive method, and a relatively large current (about 490 .mu.A) is flown therethrough. As a result, the light-emission efficiency is 0.025 lm/w (white), which implies a low efficiency, and therefore this display panel is not utilized as a color television receiver panel except for a TV receiver panel with special purposes. In this display panel, He (partial pressure ratio of 93%)-Kr (5%)-Xe (2%) gas is employed as the filling gas, and total pressure thereof is 400 Torr.
In FIG. 2, there is shown a DC type gas-discharge display panel as a second conventional display panel. It should be noted that the same reference symbols shown in FIGS. 1A and 1B are employed as those for denoting the same constructive elements shown in FIG. 2. There are other reference symbols in which symbol "AA" indicates an auxiliary anode; symbol "R-Ph" shows red phosphor; symbol "G-Ph" indicates green phosphor; symbol "B-Ph" is blue-phosphor; symbol "PS" shows a priming slit; symbol "DC" is a display cell; symbol "W" represents a wall; and symbol "ACE" indicates an auxiliary cell. The operation of this second display panel should be referred to the above-described publication (2).
In FIG. 3, there is shown a DC type gas-discharge panel according to a third conventional display panel. It should be noted that the same reference symbols shown in FIGS. 1A, 1B and 2 are employed as those for denoting the same constructive elements shown in FIG. 3. As other reference symbols, there are provided symbol "F" indicates a filter; symbol "CB" denotes a cathode bus line; symbol "WB" shows a white back; symbol "AAL" is an auxiliary anode life; and also symbol "DAL" denotes a display anode line. A detailed description of this third conventional display panel should be referred to the above-described publication (3).
Furthermore, FIGS. 4A and 4B represent a DC type display panel according to a fourth conventional display panel. FIG. 4A is a plan view of this display panel, as viewed at a display side, and FIG. 4B is a sectional view thereof cut away along a cutting line X.sub.l -X.sub.2 shown in FIG. 4A. The structure of this fourth display panel is most similar to that of a DC type gas-discharge display panel according to the present invention. It should also be noted that the same reference symbols shown in FIGS. 1A to 3 are employed as those for denoting the same constructive elements shown in FIGS. 4A and 4B. As other reference symbols, there are provided reference symbol "AC" denotes an auxiliary cathode; symbol "DAB" shows a display anode bus line; and symbol "R" indicates a current limiting resistor. A detailed explanation of the fourth conventional display panel should be referred to the above-described publications (4) and (5).
The above-described second to fourth conventional display panels are driven by the pulse memory drive method, the cathodes "C" of which are made of such materials as Ni, A1 and LaB.sub.6, and in which He-Xe (1.5 to 5%) gas is employed as the filling gas. The total pressure of the display panel is from 200 to 250 Torr.
As previously described in detail in the above-mentioned publication (1), peak luminance of an image of the first conventional gas-discharge display panel is about 33 cd/m.sup.2, namely dark. Moreover, since the light-emission efficiency is not so high, this first display panel is not adequate to a display panel for a large-screen sized television receiver.
Although no description about a lifetime of this first display panel is made in the above publication (1), a relatively long lifetime will be predicted, because the light emission duty which is inversely proportion to the line number of this display panel, is 1/480, namely low, and thus luminance thereof is lowered. Assuming now that a "lifetime" is defined by operation time during which present luminance of a display panel becomes 1/2 of initial luminance, generally speaking, when light emission duty is lowered to reduce luminance, when a comparison is made between the lifetimes of the display panels, luminance X lifetime should be employed as a comparison basis.
As to the second and third conventional display panels, the practical lifetimes may be predicted as 1,000 hours to 2,000 hours since luminance thereof is increased due to the memory function, and also peak luminance is from 50 to 100 cd/m.sup.2. Since when luminance is 100 cd/m.sup.2, 10,000 hours are required as the practical predicted lifetimes of the second and third conventional display panels constitute a big problem.
It could become appear that the most important factor to determine a lifetime of a display panel is such that luminance of this display panel is lowered since a sputtered cathode material adhere to an inside of a cell. Also, it could be recognized that since a discharge current should be reduced so as to suppress the sputtering, the sustaining discharge currents of the second and third conventional display panels are suppressed to about 100 .mu.A, but the lifetimes thereof are still short.
To improve the above-described drawback, the current limiting resistor is connected to the fourth conventional display tube, so that the sustaining current thereof is lowered and then the lifetime thereof becomes approximately 2 times longer than that of the second or third conventional display panel. However, this longer lifetime is not a practically sufficient lifetime.
As previously explained, a DC type gas-discharge display panel with high luminance and a sufficiently long lifetime could not be realized from those conventional DC type gas-discharge display panel.
In, for instance, the DC type gas-discharge display panel shown in the above-mentioned publication (5), there are employed the resistors for each of the discharge cells in order to limit the discharge currents flowing through the respective discharge cells. This resistor owns such roles that the discharge current of the discharge cell is limited to the normal glow-discharge region, sputtering is dissipated, and the memory effect is maintained in the DC memory type discharge display panel.
FIGS. 5A and 5B are schematic diagrams of a structure of this discharge display panel. FIG. 5A is a plan view of a portion of this discharge panel, and FIG. 5B is a sectional view thereof, taken along a cutting line X.sub.3 -X.sub.4. Also, there is shown in FIG. 5B a cutting sectional plane X.sub.5 -X.sub.6 in FIG. 5B. It should be noted that the same reference symbols shown in FIG. 1A to 4B are employed as those for denoting the same constructive elements shown in FIGS. 5A and 5B.
In this example, a cathode "C" is formed on a front plate "FP", both of an anode bus line "AB" and an auxiliary anode "AA" are formed on a rear plate "RP" and positioned perpendicular to the cathode "C", and also a discharge cell "DCE" surrounded by walls "W" are formed on the respective cross points between the anode bus line "AB" and the cathode "C". In the discharge cell "DCE", a resistive material "RM" having an L-shaped form is furthermore fabricated between the anode bus line "AB" and the anode "A".
Operation of this discharge display panel will now be summarized. When a predetermined voltage is applied to a specific cathode "C" and the anode bus line "AB", a current is flown via the resistor R to the cells "DCE" at these cross points, so that a discharge occurs between the anode "A" and the cathode "C". The phosphor "Ph" emits light in response to ultraviolet rays produced by this discharge. Thus, the specific discharge cell "DCE" within the panel can emit light. The light is emitted from the specific cell through the front plate FP to an outside. The red, green and blue phosphor are employed for each of the discharge cells "DCE" to display a full-colored television image. The function of the white glass back "WB" is to electrically insulate the electrode and also to derive the emitted light at the high efficiency. A discharge is previously induced between the auxiliary anode "AA" and the cathode "C" so that the commencement of the discharge in the discharge cell is emphasized via the priming slit "PS".
In accordance with the above-described DC type discharge display panel, the higher light-emission efficiency can be achieved under the small drive current, and also deterioration of the display panel caused by the sputtering can be prevented, thereby prolonging the lifetime thereof. To this end, the resistors "R" for limiting the discharge currents are employed in the respective cells "DCE".
In accordance with prior art, the L-shaped resistive materials to constitute the resistors have been separately formed with the respective cells.
A large-sized display panel is manufactured by way of, for instance, the thick-film printing method and the like. The conventional panel manufacturing method has a drawback that large fluctuation happens to occur in the resistance values, depending upon the manufacturing precision, e.g., the dimension and thickness of the resistive materials. Also, the resistance values are fluctuated in accordance with the positions and dimensions of the electrodes for terminating this resistor. If the resistance value is fluctuated, there are problems that the discharge currents of the respective cells are changed, and therefore the light-emitting outputs are fluctuated, and the fluctuated light appears as fixed pattern noise on a displayed image. In other words, there is a problem that a lack of luminous uniformity, or luminous fluctuation happens to occur in the respective discharge cells.